High availability

OpenBao can run in a high availability (HA) mode to protect against outages by running multiple OpenBao servers.

Design overview

The primary design goal for making OpenBao Highly Available (HA) is to minimize downtime without affecting horizontal scalability. OpenBao is bound by the IO limits of the storage backend rather than the compute requirements. Being bound by the IO limits simplifies the HA approach and avoids complex coordination.

Storage backends, such as Integrated Storage, provide additional coordinative functions enabling OpenBao to run in an HA configuration. Supported by the backend, OpenBao will automatically run in HA mode without further configuration.

When running in HA mode, OpenBao servers have two states they can be: standby and active. For multiple OpenBao servers sharing a storage backend, only a single instance is active at any time. All standby instances are placed in hot standbys.

Only the active server processes all requests; the standby server redirects all requests to an active OpenBao server.

Meanwhile, if the active server is sealed, fails, or loses network connectivity, then one of the standby OpenBao server becomes the active instance.

Please note that only unsealed OpenBao servers may act as a standby. If a server is in a sealed state, it cannot act as a standby. Servers in a sealed state cannot serve any requests if the active server fails.